Yeast drying apparatus



Sept. l2, 1950 A. M. FlscHl-:R 2,521,706

YEAST DRYING APPARATUS Filed Apri; 14, 1943 'l sheets-sheet 1 lNVgNToR. QefMZSc/zer A. M. FISCHER YEAST DRYING APPARATUS sept. 12, 195o 7 Sheets-Sheet 2 Filed April 14, 1943 INVENTOR. Qe/YZSC/zer BY Mae/MM l Sept. l2, 1950 A.y M. FISCHER YEAsT DRYING APPARATUS 7 Sheets-Sheet 4 Filed April 14, 1945 IN VEN TOR. QZer/flcr BY Sept. 12, 1950 A. M. FISCHER YEAsT DRYING APPARATUS '7 Sheets-Sheet 5 Filed April 14, 1943 INVEINTOR. @,be/Yfdzer.

Sept. 12, 1950 A. M. FISCHER 2,521,706

YEAST DRYING APPARATUS Filed April 14, 1943 7 Sheets-Sheet 6 llllllllllllllllllllllllHIII INVENTOR. v

mma/M Sept. 12, 1950 A. M. FISCHER YEAsT DRYING APPARATUS 7 Sheets-Sheet '7 Filed April 14, 1945 Patented Sept. 12,h 1950 UNITED STATES' PATENT oEFlcE 2,521,106 YEAs'r DRYTNG APPARATUS Albert M. Fischer, Chicago, lll. Application April 14, 194s, serial No. 483,032

(ci.` s- 11) 4 Claims. 1

The present invention pertains generally to an improved method of and apparatus for drying yeast. More particularly, the invention is directed to improved yeast drying apparatus of the revolving drum type in which the yeast is dried on the outer surface of a rotating heated drum at atmospheric pressure.

One of the principal objects of the invention is to provide yeast drying apparatus of this general type which is suitable for automatic operation in the drying of brewers surplus yeast.

Another object of the invention is to provide an improved yeast drying apparatus and method which will preserve to the maximum degree the heat labile vitamins and other food values in the yeast, and which will produce a purer dried brewers yeast of higher vitamin potency.

In this regard, one of the more important objects of the invention is to provide an improved circulation of the yeast or an improved method of handling the yeast in the operating cycle of the apparatus, whereby to avoid objectionable overheating of the yeast and objectionable overexposure of the yeast to the atmosphere and thereby oxidation, during the time that the yeast is still in the liquid state and is being circulated through the apparatus or is being made ready for the actual drying on the drying drum. I have found that this is quite important in order to preserve to the maximum degree the heat labile vitamins and other food values in the yeast. The yeast passes through four temperature stages in the complete cycle of my irnproved method. The first temperature is the storage temperature, the second is the intermediate or preheated temperature, the third is the temperature in the circulation stage, and the fourth is the drying temperature. The storage temperature is usually quite low, being generally in the neighborhood of 33 F., so as to inhibit fermentation and/or autolysis of the yeast. However, the yeast is of relatively heavy consistency at this low temperature and it is diihcult to circulate it through the apparatus, difficult to screen, etc. Accordingly, my improved apparatus and method embodies the step oi raising the yeast to an intermediate temperature before application to the drum. This intermediate or preheated temperature is preferably' in the neighborhood of 160` F., although substantial deviations may be made in either direction from this temperature is desired. The preheated circulating volume of yeast is pumped into a dip trough or feed trough through which the lower periphery of the drum revolves, and it is here that the yeast is brought into direct contact with the drying drum or into immediate proximity thereto. This, of course, raises the temperature of the yeast to about and for this reason the quantity of yeast in circulation should be as small as possible, thereby assuring a speedy conversion to the dry state and lowering of the temperature to that of the surrounding atmosphere. Such portions of the circulated volume as do not adhere to the surface of the drum, or are wiped off the drum by the equalizer which prevents an excessive thickness of lm accumulating on the drum, are carried over or are dropped into a spill trough from which they flow back to the circulating compartment. As successive quantities of yeast adhere to the drum, so that the circulated volume gradually becomes depleted, the reserve or storage volume of preheated yeast automatically feeds into this circulated volume of preheated yeast so as to maintain an adequate volume for circulation. However, this circulated volume is substantially smaller than the reserve or storage volume of preheated yeast, and accordingly only a relatively small circulated volume is subjected to contact with the high temperature of the drying drum, and to contact with the atmosphere. The drying drum preferably operates at a temperature in the neighborhood of 300 F., which can deleteriously aect heat labile vitamins in the yeast if the liquid yeast is continuously or recurrently circulated into contact with the drum over substantial periods of time before the yeast actually adheres to the surface of the drum in the drying step of the cycle. This deleterious action of the high temperature of the drum on vitamin potency is avoided or minimized by the aforementioned method of dividing the preheated batch of yeast into a substantial reserve volume and a relatively small circulating volume, and only bringing the smaller circulating volume into contact with the drum.

The preheating step of the cycle is also advantageous for screening the yeast. It may be desirable to remove trub and hop resins from the yeast by screening, and this is greatly facilitated by preheating the yeast to obtain ready flow through the screens. Such avoids the objectionable procedure of adding water to the yeast to secure iiow through a screen, and having to remove this excess water in the subsequent drying process.

Another object of the invention is to provide an improved manner of applying the liquid yeast to the cylindrical surface of the drum in the form of a thin film.

Another object of the invention is to provide 3 improved equalizing apparatus for distributing and equalizing the thickness of the 111m of yeast over the surface of the drum.

Another object of the invention is to provide an improved construction and arrangement of scraper blade mechanism for stripping the dried yeast from the drum. Thismechanism includes improved adjustments for adjusting the scraping blades relatively to the drum. It also includes improved lifting apparatus for moving the scraping blades into and out of operative engagement with the drum, the movement of the several blades back into engagement with the drum being a sequential operation in which the blades engage the drum successively instead of simultaneously in order to avoid the placing of an abrupt or abnormal load on the machine.

Other objects, features and advantages of the invention will appear from the following detail description of one preferred embodiment of the apparatus and one preferred method of carrying the invention into effect. In the accompanying drawings illustrating such embodiment:

Figure 1 is an end elevational view of the machine, some of the associated apparatus being illustrated schematically;

Figure 2- is a side or front elevational view of the'machine, a portion of the conveyor trough being broken away to show the conveyor screw;

Figure 3 is a fragmentary side view of the preheating chamber, illustrated partly in section to show the reserve compartment'and the circulating compartment;

Figure 4 is an end view of the preheating chamber, also showing the dip trough and the spill trough in section;

Figure 5 is a fragmentary end view showing the mounting of the dip and spill troughs, and also showing the relation of the equalizer to the spill trough; Y

Figure 6 is a fragmentary plan view of the latter arrangement;

Figure 7 is a fragmentary plan view of the equalizing mechanism for distributing and equalizing the film of yeast on the drying drum, and for predetermining the thickness of said nlm:

Figure 8 is a transverse sectional view taken approximately on the plane of the line 4 4 of Figure 7;

Figure 9 is a detail sectional view taken on the plane of the line 9--9 of Figure 8;

Figure 10 is a fragmentary elevational view of one of the end Scrapers;

Figure l1 is a detail sectional view taken on the plane of the line of Figure 10;

Figure 12 is a fragmentary front elevational view of the scraper blade mechanism;

Figure 13 is an end view thereof;

Figure 14 is a horizontal sectional view taken approximately on the plane of the line |4|4 of Figure 12;

Figure 15 is a detail section taken on the plane of the line |5| 5 of Figure 12; and

Figure 16 is a section similar to Figure 15 but taken at another point along the scraper blade mechanism.

Referring first to Figures 1 and 2, the heated drying drum is indicated at 2|, this drum being hollow for the circulation of steam or other heating medium therethrough. Secured to opposite ends of the drum are supporting -trunnions 22 and 22 (Figure 2) which are .iournaled for rotation in bearings 24 and 25 which aremounted on the end standards 26 and 21 of the supporting frame 28. 'I'he bearings 24 and 25 are preferably of the self-aligning type so as to facili* tate assembly and minimize bearing wear. The bearing shaft 22' of the left hand trunnion 22 carries a large spur gear 3| which is driven by a driving pinion 32 which is adapted to be driven at any selected speed through a variable speed drive mechanism 22, the latter receiving its power in-put from an electric motor or other driving source. The ability to adjust the speed of rotation of the drum 2| through the instrumentality of the variable speed unit 22 enables the apparatus to be adjusted to different temperatures, humidity conditions, and other operating conditions.

Steam for heating the drum 2| is conducted through supply pipe 26 to a manifold housing 21 which is assembled over the end of the right hand'trunnion shaft 22'. This right hand trunnion shaft is hollow for the circulation of steam therethrough into the rotating drum 2|, and the inner end of the manifold housing 21 is provided with an adjustable stuffing gland Il for maintaining a steam-tight joint at this point .where the manifold housing engages over the end of the rotating trunnion shaft 22'. The discharge of condensate and exhaust steam from the drum occurs through a discharge pipe 2l which passes axially through the hollow trunnion 23' in spaced relation to the bore of this hollow trunnion. As indicated in dotted lines, the inner end of this discharge or condensate pipe 22 is provided with a downwardly extending end 3l' or any other equivalent device which is adapted to draw the condensate and exhaust steam from the lower interior portion of the drum, these devices being well known and serving to prevent the accumu lation of an excessive amount of condensate within the drum. The discharge pipe 22 rotates with the drum and has its outer end extending' into manifold housing 31. this outer end being surrounded by an adjustable stumng gland 4| carried by the manifold housing 31. Said manifold housing has attachment to the end frame member 21 through a mounting bracket 42. A drain pipe 42 screws into the outer member of the stumng gland, in communication with the condensate pipe 29, and conducts the condensate and discharge steam from the end of said condensate pipe down to a T connection 44. Leading from the lower end of T.connection 44 is a vent valve 45 which acts as a vent for the drying drum 2| and which serves to discharge condensate, even in the absence of steam pressure. Leading from the lateral port of the T connection 44 is a pipe 48 which is adapted to conduct condensate and exhaust steam into a steam trap 41. From this steam trap the condensate is conducted to the heating jacket of a preheating chamber disposed below the drum 2|, as I shall nowdescribe.

This preheating chamber, designated Il in its entirety, is ci' approximately V shaped trough formation (Figure 1) disposed directly below the drying drum 2| and detachably mounted by suitable slide brackets to the end frame members 2| and 21. 'Ihese slide brackets enable the chamber Il to be slid sidewise out from under the drum. Surrounding the bottom and both sides of this preheating chamber is a heating jacket Il which receives condensate at its lower right hand end through pipe 54, leading from the outlet end of the steam trap 41. The condensate is discharged from the heating jacket l2 at an elevated point adjacent to its left hand end through waste pipe li (Figure l). As shown in Figures 2 and 3, the preheated chamber Il is divided by a transverse partition 61 into two longitudinally spaced compartments lla and 5|b, compartment 6|a being a heated storage compartment for the yeast, and compartment IIb being a heated circulating compartment for the yeast. A spill opening 68 extends through the partition 51 at a relatively high level (Figure 3) so that the heated yeast at the upper level of the batch in the storage compartment 5|a overflows through said opening into the circulating compartment 6|b. As shown in Figure 2, an agitator 59, of the propeller or any suitable type, is mounted at the left hand end of the storage compartment Sla for impelling a circulating flow of yeast toward the partition 51, the floor of this storage compartment 5|a sloping downwardly toward said partition for draining purposes. The shaft 6| of the propeller agitator 59 extends out through a gland packing in the end of the compartment 5| and carries a sprocket wheel 62 at its outer end. Trained over this sprocket wheel is a sprocket chain 63 which passes over an intermediate transmission sprocket 64 (Figure 1) mounted on a stub shaft 65 projecting from the end frame 26. The sprocket wheel 64 is driven by a relatively small sprocket pinion 66 secured thereto, over which sprocket pinion is trained a main drive chain 61. The chain 61 passes up over a relatively large driving sprocket 68 which is mounted on the left hand trunnion 22' of the rotating drum, said main chain also passing around a pinion 69 which drives the feeding screw of the conveyor, as will be later described. 'Ihe ratio between the large driving sprocket 68 and driven sprocket 66, and the ratio between the driving sprocket 64 and driven sprocket 62, are such that the agitator propeller 59 is rotated at a relatively high speed, compared to the slow rotation of the drying drum 2 l.

The yeast is supplied at a relatively cold state to the preheating chamber 5| from a low temperature storage vat 1|, as shown in Figure 1. This storage vat stores the brewers surplus yeast which results as a by-product of the brewing operation, and such vat may be located on a different iloor level of the brewery than the yeast drying apparatus. A fluid' pump 12 driven by the electric motor 13 draws the cold yeast from the vat 1| and pumps the same up through the supply pipe 14 to the preheating chamber 5l, preferably discharging into the storage compartment 5|a at a point adjacent to the propeller agitator 59. The yeast is drawn from the low temperature vat 1| at a temperature of approximately 33 F., and, accordingly. the pump 12 is preferably oi the positive displacement rotary type to handle the viscosity of the yeast at this temperature, the pump also being oi a type of preclude gravitational iiow therethrough in situations where the storage vat 1i may be at a higher level than the preheating chamber 5l. The operation of the pump motor 13 is governed by a iioat control switch which responds to the level of the yeast in the circulating compartment SIb, as I shall now describe.

As the yeast becomes heated in the preheating compartment 5|a, it rises to the level of the overilow opening 58 and spills ove;` into the circulating compartment 5| b. From here the yeast flows down through take-off pipe 11 to a circulating pump 18 driven by electric motor 19. Because of the more fluid state of this preheated yeast (preferably ranging between 150 to 200 F.) the pump 18 may be a centrifugal pump, al-

though a positive displacement pump may be employed if desired. The outlet of said pump is connected with pipe 8| in which is interposed a throttling valve 82 for governing the rate of circulatory flow of the preheated yeast to the dip or feed trough 84. A 3way valve 85 may lbe interposed in the take-off pipe line 11. 'I'he dip or feed trough 84 is best shown in Figures -4 and 5. from which it will be seen that it is of open top arcuate form and is positioned immediately below the drying drum 2| so that the periphery of this rotating drum dips down into said trough for picking up yeasttherefrom. The dip trough is suspended between two horizontal tie rods 91 and 88 extending between the ends frames 26 and 21 on each side of the drum 2|. As best shown in Figure 5, supporting arms 89 project to the left from each end of the dip trough and carry vertical mounting bosses 9| at their ends. Studs 92 extend up through these bosses and tap into collars 93 which are rotatable about the supporting rod 91. Nuts 94, threading over the lower ends of the studs 92, serve to secure the mounting bosses 9| to the collars 93. At the opposite side the dip trough is provided with similar supporting arms 89 carrying forked yokes 9|' at their ends for engaging over studs 92' which thread up into collars 93 rotatably mounted on the outer supporting rod 98. Wing nuts 94' releasably hold the forked yokes 9| over the studs 92. By merely releasing the wing nuts 94. at each end of the dip trough, the trough can be swung down to a relatively accessible position for the purpose of cleaning out the trough at predetermined intervals or after the running of a Ipredetermined batch. The feed pipe 8| which conducts the yeast up from the pump 18 into the dip trough 84 has an easily releasable coupling interposed therein near the trough, which enables the pipe to be disconnected from the trough when the trough is to be swung down into its lower position for cleaning.

The rotation of the drying drum 2| down through the dip trough 84 tends to carry yeast up over the right hand edge 95 of the dip trough, as viewed in Figure 4. To catch this overflow or spill portion of the yeast, the feed trough 84 is formed with a smaller spill trough 96 extending along its right hand edge. This righthand spill edge 95 is lower than each of the edges around the other three sides of the dip trough 8d so that all excess yeast pumped into the dip trough spills over this overflow edge 95 into the overflow trough 96, in addition to the yeast which is carried by the drum periphery over into the overiiow trough. An equalizing blade 98 extends along the entire length of the drying drum 2i for equalizing and predetermining the thickness of the yeast film carried upwardly on the surface of the drum. This equalizing blade is preferably adjusted to a. position spaced a relatively minute distance from the drum, so that only a thin lm of yeast is carried upwardly by the drum beyond this equalizing blade. Such equalizing blade is positioned above the overow trough 96 so that all excess yeast which is stripped from the drum by the equalizing blade drops down into the spill trough 96. The apparatus for adjustably mounting the equalizing blade 98 will be later described. It will be seen from the foregoing that the spill trough 96 functions (1) to receive the excess yeast which spills over the overflow edge irrespective of motion of the drying drum, (2) to receive excess yeast which is carried up on the periphery of the ro- 7 tating drum and which falls from said periphery before encountering the equalizing blade, and (3) to receive the excess yeast which is stripped from the predetermined film on the drum by the action of the equalizing blade ll.

The -excess yeast accumulating in the spill trough 96 may be immediately returned by a direct path to the circulating compartment lib of the preheating tank 5I, for prompt recirculation through the circulating pump Il hack to the dip trough Il; or this excess yeast in the spill trough may be conducted through a separate screening path to suitable screening apparatus, from whence the screened yeast is then conducted back to the circulating compartment Sib for recirculation through pump 1t up to the dip trough 84 again. Referring to Figure 4, a return pipe 99 leading from the spill trough conducts the excess yeast to two valves ill and Ill. Any suitable arrangement of releasable coupling 99 enables the spill trough to be released from the piping for downward swinging movement with the dip trough 8|, Opening the valve I" causes the excess yeast to take the direct path through pipe llt immediately back to the circulating compartment SIb. Opening the other valve IM causes the excess .yeast to take the screening path through pipe Il! to the two screening units |03 and IM. A return pipe I 02a in the screening circuit returns the yeast from the screens Il), |04 to the circulating compartment SIb. A fractional opening of both valves |00 and IM may be resorted to for causing part of the yeast to take the direct return' path and part to take the screening return path. Screening of the yeast is frequently desirable or essential in order to obtain the most satisfactory quality of dried yeast. For example, in soule situations the yeast may contain an objectionable amount of trub and hop resins which it is desirable to remove. To remove these substances the yeast usually-has to be passed through a screen of approximately 40 or 50 mesh. When the yeast is in a cold state, as exemplified by the condition of the yeast when it is pumped from the low temperature storage vat 1|, its consistency is too heavy to be passed through such a screen, at least without the addition of a substantial quantity of water. When following such prior procedure of adding water, the quantity of water to be added must at least be equal to approximately the weight of the yeast. The added surplus water has to be removed, either -by settling out of the yeast and decanting of the supernatant water, or by mechanical separation, or by separate evaporation in a vacuum pan. or during drying. Some yeasts do not settle out at all and stay in suspension so that mechanical separation or evaporation becomes a necessity. It will be noted that by interposing the screening units I" and lll in that part of the circulatory path oi the system which handles the yeast in a preheated state, the aforementioned dilution with water can be completely avoided. My improved process of producing a puried dried brewer's yeast utilizes the fact that wet yeast, upon heating, re-

leases part of its cell content, and, therefore,

screen Il! and llt, which may be of the same mesh or of different mesh. Separate control valves Ill and lill govern the iiow to the two nlters, and a shut-oil.' valve lll is interposed in the return portion Illa of the circulating pipe Il! which conveys the strained yeast back to the circulating compartment IIb. A cross-connection Ill between the two separatingdevices Ill and I is provided so that in the event the screening or separating element in one of these devices becomes clogged the yeast will automatically overflow through the cross-connection Ill into the other device and pass through its screening or separating element. The capacity ot the circulatingpump 18 is preferably such that the entire volume of yeast in the circulating compartment SIb can be pumped over the screen or screens in the separating units approximately once every three minutes. It will hence be seen that any trub and hop resins arriving in the preheating tank Il can therefore be screened out within a short time.

The supply of yeast to the preheating compartment 5Ia, and the liquid levels in the preheating compartment 5 Ia and in the circulating compartment Bib are governed by a oat controlled switch H2. This oat controlled switch comprises a swinging float ||2a mounted in the circulating compartment Sib to respond to the level of yeast therein, this swinging float being connected through suitable operating linkage ||2b with an electrical switch Il2c. The operating relation is such that when the float II2a falls to a predetermined level, the switch i|2c is closed. and when the float rises to a predetermined level the switch is opened. The -pilot switch IIZc governs a pilot circuit IM which controls the energization of an electromagnet Ill serving to actuate a power switch H6. The power switch IIB controls the connection of the power circuit H1 to the electric motor I3 which drives the yeast supply pump 12. The pilot circuit IM may tap oil the power circuit Ill. The operating relation is such that when the level of the yeast in the circulating compartment 5Ib falls to a predetermined low point, the descending float iIZa closes the pilot switch IIZc and operates through the electromagnet lli to close the power switch H6. Thereupon the electric motor 13 drives the supply pump 12 to pump an additional quantity of yeast from the storage vat Il to the preheating chamber 5| so that more of the preheated yeast will ow from the preheating compartment ila through the spill opening il into the circulating compartment IIb. When the quantity of yeast in the circulating compartment Sib is restored to its desired high level, the rising of iloat Illa will open the pilot switch I lZc and, in turn, open the power switch H6 to interrupt continued feed of yeast to the preheating chamber.

Referring to Figure 3, a connecting valve or cock lzl is provided adjacent to the bottom of the partition i1 so as to establish communication between the preheated storage compartment ila and the preheated circulating compartment Bib at the end of a yeast drying operation. This cock is actuatable by an operating handle |22 accessible at the top of the preheating tank Il. When approaching the end of a given batch oi' yeast or the end of a predetermined yeast drying cycle, the cock l2! is opened so as to drain substantially all of the preheated yeast from the storage compartment Bia into the circulating compartment Mb, thereby enabling substantially all of the yeast in both compartments to be circulated up to the dip trough 54 for application to the drying drum. As a very sensitive switch is employed, the liquid level in the compartment |b is maintained within V8 inch, thereby avoiding variations in the temperature of the yeast in the circulating compartment.

Referring` again to the equalizing blade 35 which predetermines the thickness of the film of yeast adhering to the drying drum, the adjustable mounting for this equalizing blade is illustrated in Figures '1, 8 and 9. Said equalizer blade is preferably one or more long, thin strips of stainless steel secured by screws |25 to a backing bar |26. At spaced points along its length this backing bar |26 is secured by screws |21 to mounting arms |28 which are carried by a rotatable mounting shaft |23. Said shaft |25 is journaled in bearing brackets |30 secured to the end frame standards 26 and 21. The hub |3| of each mounting arm |25 is adjustably secured to the shaft |23 by one or more set screws |32. By loosening these set screws and separately adjusting the mounting arms |26, the backing bar |26 may be shifted until it is parallel to the drum. Still further, the mounting screws |25 pass through elongated slots in the equalizer blade 38, so that by loosening these screws the blade, or any portion thereof, may be shifted upwardly or downwardly relatively to the backing bar |26. Thus, the equalizing blade may be minutely adjusted at different points along its length so as to maintain a relatively accurate predetermined spacing from the surface of the drum. The thin stainless steel blade projects substantially beyond the mounting bar |26 so that the stripping edge of the blade has some resiliency relatively to the mounting bar, and hence can yield if it should be pressed against the surface of the drum.

The equalizing blade can be adjusted toward or away from the drum to vary the thickness of the adhering film of yeast by the manipulation of a hand wheel |35. This hand wheel is provided with an internally threaded hub |36 which is adapted to screw back and forth along a threaded shaft or pintle |31 as the hand wheel is rotated. The inner end of this threaded shaft passes through a vertical slot |38 in the adjacent flange of the frame standard 21, and is formed with a pivot eye |39 at its inner end. A shouldered pivot stud |4| screws into a tapped hole in the transverse flange of the end standard, and has its outer end passing through the pivot eye |33 and receiving a nut |42 on its reduced end. Such mounting of the threaded shaft |31 holds the shaft against axial rotation but enables it to oscillate vertically around the pivot stud |4|. A shifter collar |45 is coupled to the hub o1' the hand wheel |35 by the split halves of a coupling collar |46 which compel the shifting collar |45 to move endwise with the hand wheel but do not compel it tc rotate therewith. The collar halves |46, |46 are formed with inwardly extending iianges |41 which seat in an annular groove |45 formed in the shifter sleeve |45. Screws |43 detachably secure the collar halves |46, |46 to the hub portion |36 of the hand wheel. end of the shifter collar |45 has two trunnion pins |5| projecting outwardly from opposite sides thereof. Secured to the adjusting. shaft |23 is an actuating arm |52 which is formed with spaced yoke arms |53 at its upper end arranged to embrace the shifter sleeve |45. Slots |54 extend in laterally from one side edge of each yoke The inner y 10 arm, and the trunnion pins |5| seat in the bottoms of these slots. A retaining plate |55 is then secured over this edge of each yoke arm by cap screws |56. Each of these retaining plates has a lug portion extending inwardly into its slot |54 for confining the -trunnion pins in the lower ends of said slots. The above described construction establishes a close fitting operating connection between the shifter sleeve |45 and the actuating arm |52 so that there will be no play between these parts to destroy minute adjustments o! the equalizing blade 96. It will be evident that as the hand wheel |35 is screwed outwardly or inwardly along the threaded shaft |31, the equalizer blade 98 will be adjusted toward or away from the drying drum 2|, the threaded shaft |31 swinging vertically around the pivot stud |4| to accommodate the angular motion of the actuating arm |52.

By reason of the fact that the drying drum 2| is dipping down into the dip trough 84 in its continuous rotation, it necessarily picks up liquid yeast on each of its end surfaces. This has'the advantage of increasing the evaporating surface of the drum, corresponding to the areas of these end surfaces immersed in the yeast. However, the accumulation of yeast must be removed from these end surfaces, otherwise it will continue to cake thereon to an objectionable thickness. Figures 10 and 11 illustrate an improved form of end scraper, designated |51, employed at each end of the drum for removing the end lm of yeast. This scraper is in the form of a spring steel blade which has its outer end riveted to an adjustable bracket |58 secured by cap screws |53 to the nearby leg of the adjacent end frame 25 or 21. 'I'he bracket |58 has enlarged circular holes or elongated slots |58' for receiving the cap screws 53, whereby to facilitate adjustments in the angle and tension of the scraper blade. The scraper is preferably adjusted so that its contact against the end of the drum produces hardly any friction. For this purpose, the circular outer area of each drum head p ssing through the liquid yeast must be accuratel machined so that the scraper blade |51 will have a smooth machined surface against which to bear. It will be understood that the outer cylindrical surface of the drum also has a smooth machined and ground surface. Projecting laterally inwardly from the lower portion of the end scraper |51 is a small auxiliary equalizer |51a which acts to equalize or prevent objectionable accumulations of yeast on the peripheral surface of the drum adjacent to the end heads. This auxiliary equalizer has its operating edge spaced from the periphery of the drum a distance corresponding to the desired thickness of yeast film on the drum. When the yeast is removed from the end of the drum by the end scraper |51, some of the liquid yeast will accumulate on the edge and will flow by gravity to the cylindrical surface of the drum and will work back along the cylindrical surface an appreciable distance. Inasmuch as the cylindrical surface is already covered with yeast at this point, the additional yeast coming from the end scraper will not dry by the time it reaches the scraper blades or knives at the far side of the drums rotation. The auxiliary equalizers |51a avoid this condition by spreading excess yeast from the cylindrical surface of the drum adjacent to the end heads,A thereby enabling it to dry by the time it reaches the scraper blade. The yeast which is removed from the left hand end of the drum 11 by the scraper and equalizer |51|51a at this end of the machine drops down into the preheated storage compartment Bla, for recirculation back into contact with the drum, while the yeast which is removed from the right hand end of the drum by the scraper and equalizer IST- lila at this end of the machine drops down into the preheated circulating compartment |b, and possibly into the spill trough 86 as well, also for recirculation back into contact with the drum. This yeast is partly dehydrated and is removed from the ends of the drum in cake-like consistency. It will thus be seen that the two end surfaces of the drum are utilized as drying surfaces for increasing the dried content of the liquid material being circulated into contact with the drum.

Referring now to the scraper blade mechanism for removing the dried yeast from vthe drying drum, this mechanism is indicated collectively at |68 in Figures 1 and 2, from which it will be seen that it extends across the front of the machine to bear against the lower front side of the drying drum. The scraper mechanism is assembled on a rotatable mounting shaft ISI which extends parallel to the drying drum adjacent to the lower front side thereof. 'I'he ends of this shaft are journaled in bearing bosses |62 which are formed integral with webs Il! projecting outwardly and upwardly from adjustable mountlng brackets |64. Each mounting bracket |64 is secured by bolts |85 to the front flange of its respective end frame 2l or 21. 'I'he bolts |85 pass through vertically extending slots I in the mounting bracket I il, whereby the mounting bracket can be shifted upwardly or downwardly to dinerent adjusted positions along the inclined front flange of the end frame. This vertical adjustment of the mounting brackets and of the mounting shaft ISI enables the angle between the scraper blades or knives and the cylindrical surface of the drum to be adjusted as desired, i. e., to adjust the intercepted angle between the scraper knives and the surface of the drum as viewed from the end of the machine. The scraper knife means |68 is preferably divided into a plurality of blade lengths disposed approximately end to end along the length of the drying drum. By dividing the knife apparatus into a purality of sections these sections can be arranged to engage the drum progressively so as to reduce the shock load when starting up the operation of the machine, and the sections are also easier to adjust relatively to the drum, and are cheaper to make and sharpen. In the illustrated embodiment I have shown the knife assembly divided into three knife sections, consistlng of a middle knife |6811 and two end knives |i8a and |680 on each side thereof. The middle knife |6811 is disposed slightly higher than the end knives so that it can overlap the adjacent extremities of the end knives and thereby avoid leaving any line of the drum which is not stripped by a scraping knife. Each knife section is mounted by substantially the same form of mounting holder or bracket and associated cover plate, and hence I shall only describe one of these assemblies. Each mounting bracket or holder l" comprises a tilted plate portion |1| which extends horizontally substantially the length of its individual knife or blade. A right angle flange |12 projects outwardly from the lower edge of the plate portion |1|, preferably along substantially the entire length of the holder. Adjacent Lto each end of the holder circular 12 bosses |13 are formed integral with the plate and shelf portion |1||12 and project rearwardly for mounting on the adjustable supporting bar or shaft |8|. These mounting bosses |13 are freely rotatable on the mounting shaft IBI. Lugs |14 projecting inwardly from the mounting bosses |13 are apertured at |15 for receiving the hooked upper ends of tension springs |18 extending downwardly for attachment to spring tensioning devices which I shall presently describe. The action of these springs is that of continuously urging the scraper blades |68a|68c resiliently against the surface of the drying drum.

Each knife or blade is assembled against the front face of the plate portion |1| and is secured thereto by a clamping cover |18. Referring to Figure 12, each knife or blade lila-Nac is provided with downwardly projecting extensions or clamping lugs |18, as indicated in dotted lines. These extensions are provided with vertical slots |8| adapted to receive the Shanks of cap screws |82. These -cap screws pass through circular holes in the cover plate |18, and then pass through the vertical slots |8|, and then tap into threaded bores in the upwardly extending flange portion |1| of the blade holder |69.

Provision is made for effecting three different scraping adjustments of each scraper blade relatively to the surface of the drum: viz, (i) an independent adjustment of either end of the blade toward or away from the drum substantially in the plane of the blade or in a plane parallel thereto; (2) an independent adjustment of either end of the blade toward or away from the drum in a plane substantially at right angles to the plane of the blade; and (3) an adjustment of the angle intercepted between the plane of the blade and the surface of the drum, this angle being indicated at .r in Figures 15 and 16. The first of these adjustments, made in a plane coincident with the plane of the blade, or in a plane parallel thereto, is effected by the two downwardly extending adjusting screws |84 provided at each end of the blade holder |69. These adjusting screws thread through tapped bosses projecting down from the lower edge of the blade holder |68, the upper ends of these screws passing up through the step flange |12 and abutting against the lower edges of the slotted lug extensions |18 projecting down from the blade. It will be evident that upon loosening the clamping screws |82 the adjusting screws |84 can be operated selectively to shift either the left hand end or the right hand end of the blade upwardly or downwardly across the face of the mounting flange |1|, thereby adjusting the cutting edge of the blade at either end toward or away from the surface of the drum in a plane coincident with the plane of the blade. After the desired adjustment has been obtained in this plane, the clamping screws |82 are then retightened to retain the blade in its set adjustment.

The second adjustment which occurs in a plane substantially at right angles to the plane of the blade is effected by a plurality of small adjusting screws |86 extending in a horizontal row across the upper edge of the cover plate |18. These adjusting screws thread into tapped bores in the cover plate |18, and are provided with lock nuts |81 adapted to abut against the outer surface of the cover plate. The inner ends of these adjusting screws are adapted to be forced against the outer surface of the blade or knife |68a-|58c. whereby to flex any desired portion of the blade toward or away from the surface of the drum in a plane extending at right angles to the plane of the blade. These adjusting screws |86 enable relatively minute adjustments of each blade to be made relatively to the surface of the drum. In practice, I place a source of light in the space between the back side of each blade and the surface of the drum, and then actuate the adjusting screws |64 and |86 until all points along the entire edge of the blade are in such accurate contact with the surface of the drum that no light passes therebetween. The third adjustment for varying the intercepted angle a: (Figures 15 and 16) is effected by loosening the bolts |65 and sliding the mounting brackets |64 for the mounting shaft |6| upwardly or downwardly along the inclined side surfaces of the end frames 26 and 21, the slots |66 in the bracket |64 permitting such up and down sliding adjustment. Because of the angular slope of the front surface of each end frame 26, 21, and the angular relationship between the other parts of the assembly, this shifting of the mounting shaft |6| enables the blade to be adjusted for a greater or lesser intercepted angle x. The angle a: can also be adjusted by turning the two screws |84. These screws will move the blades up or down, thereby decreasing or increasing the angle x. The screws |84 serve also to compensate for wear on the blades due to regrinding or sharpening. Either bracket |64 can be adjusted independently of the other, so that either end of the mounting shaft |6| can be adjusted slightly relatively to the other end.

The aforementioned tension springs |16 act on each end of the blade holder and tend to hold the blade against the drum with a resilient pressure during the scraping operation. As shown in Figures 12 and 13, the lower ends of these springs are hooked to eye bolts |9| which pass down through apertures |92 in a channel bar |93 and thread through tapped bosses of adjusting nuts or knobs |94, the latter bearing against the under side of the channel |93. The ends of the channel |93 are secured by bolts |95 to lugs |95a projecting from the webs |63 of the mounting bracket |64. Adjustment of the nuts or hand wheel knobs |94 enables the tension of the spring |16 to be increased or decreased for causing either end of the scraper blade to be pressed with a greater or lesser pressure against the surface of the drum'.

At the conclusion of an operating cycle it is preferable to swing the blades |68a-|68c outwardly to inoperative positions, out of Contact with the drying drum. This is accomplished by rotation of a hand wheel |96 disposed at the right hand end of the machine. This hand wheel revolves a threaded shaft |91 provided with a spherical head |98 at its inner end, this spherical head seating in a spherical socket |99 formed in a bracket 20| which is bolted to the end frame 21, such mounting of the shaft |91 permitting the shaft to rotate and also to swing upwardly and downwardly through a limited arc. The threaded shaft screws through a threaded bore in a horizontally extending trunnion pin 202. The ends of the trunnion pin are journaled in the forked upper end 203 of an actuating arm 204 which is pinned to the mounting shaft |6|. It will hence be seen that rotation of the hand wheel |96 is operative to oscillate the mounting shaft |6|. Such motion of the mounting shaft is adapted to lift the blades |69a|68c progressively from the surface of the drum through the instrumentality of three different lifting arms 205, 206 and 201 which are set to act in sequence on the respective 14 blade holders. Each lifting arm is formed as an integral upwardly projecting extension from Aa collar 205', 206' and 201. Each of these collars is fixedly secured to the mounting shaft |6| by a set screw 209 (Figure 12). The lifting arm 205 is positioned to lift blade |68c from the drum; the lifting arm l206 is positioned to lift blade |661: from the drum; and the lifting arm 201 is positioned to lift the blade |68a from the drum. vAs shown in Figures 15 and 16, the arm 205 normally stands spaced a slight distance from the plate portion |1| of its respective holder, and the other two lifting arms 206 and 201 normally stand at increasingly greater distances from the flanges |1| of their respective holders. Hence, these lifting arms come into action progressively for lifting the scraping blades progressively from the surface of the drum, and, conversely, in the operation of restoring the blades to scraping position the'blades engage the drum successively, thereby minimizing any possibility of imposing an abrupt or shock load on the drum and driving mechanism. When the drying machine is started up after having been shut down for a substantial interval, it is desirable that the drying drum be rotated slowly while it is being brought up t0 temperature by the steam entering through supply line 36, this preliminary rotation serving to bring about uniform heating and expansion of the drum surface. During this preliminary rotation the scraping blades or knives should not be allowed to contactthe drum inasmuch as there is substantial likelihood of damaging the surface of the drum if the scraping blades are permitted to press against the drum when the drum is not carrying any protective film of yeast. As the yeast is brought into contact with the drum,

there may result several idle revolutions of the drum in arriving at proper operating temperatures, adjustments of the equalizer blade 98, etc. This may result in a relatively thick lm of yeast becoming encrusted on the drum before the scraping knives |68a|68c are brought into contact with the drum. If the knives were all allowed to engage the drum simultaneously, against this relatively hard encrusted film of yeast, there would result a substantial shock load in the operation of the machine. This is objectionable and is entirely avoided by the above described arrangement of the lifting fingers which `result in the blades being brought into operative engagement with the drum in a progressive sequence so that only one blade is brought to bear against the encrusted lm at one time.

As the dried yeast is stripped from the surface of the drum it falls outwardly over the outer surfaces of the scraping blades and drops down in the form of shreds into a longitudinal conveyor 2|0 which extends along the front side of the machine below the scraping blades (Figure 1). Front and rear deilector panels 2|I and 2|2 direct all of the yeast down into the conveyor. A feed screw 2|3 extends along the arcuate bottom' surface of the conveyor trough, and serves to propel the dried yeast toward one end of the trough. A cooling jacket 2|4 embraces the lower portion of the trough and is provided with suitable pipe connections 2|5 and 2|6 (Figure 2) for conducting cold water or other cooling medium through said jacket. It is desirable to cool the dried yeast before it is fed to the pulverizer. The left hand end of the feed screw 2 I3 is provided with a shaft 2|1 projecting beyond this end of the conveyorA trough 2|0. The shaft 2H carries a sprocket wheel 2|8 over which passes the drive chain 61 whichv is driven by the sprocket wheel ll on the trunnion shaft 22' of the drying drum. The feed screw 213 conveys the ilaked yeast toward the right hand end of the trough, from whence the yeast is conveyed in any suitable manner to a pulverizer or to a place of storage. In typical or preferred installations, the trough 2li is arranged to discharge into an elevator which carries the pulverized yeast up to an elevated inlet of a motor-driven pulverizing unit which breaks up the naked yeast into very small particles. From this pulverizer the yeast can be conveyed to a place of storage, or can be packaged in bags, boxes or the like.

While I have illustrated and described what I regard to be the preferred embodiment of my invention, and the preferred method of carrying the invention into effect, nevertheless it will be understood that such are merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention.

'I'he feature of my improved adjustable scraper blade mechanism is being made the subject matter of a divisional application.

I claim:

1. In drying apparatus, the combination of a rotating drying drum, a dip trough into which said drum dips, means for preheating the liquid material, a circulating chamber for the preheated liquid material, circulating means for causing the preheated liquid material to flow from said circulating chamber to said dip trough, and for causing the excess liquid material to ilow through a return path back to said circulating chamber,

means for keeping the liquid material in the cir-A culating chamber automatically at a desired level, and screening means interposed in said return path for screening the liquid material while the latter is in a preheated state.

2. In apparatus for drying brewers surplus yeast, the combination of preheating means adapted to receive the liquid yeast from a source of supply and to preheat the same, said preheating means comprising a preheating storage compartment and a circulating compartment, said storage compartment discharging into said circulating compartment, a float responsive to the level of the liquid yeast in said circulating compartment, means responsive to said float for controlling the flow of yeast from said source of supply to said storage compartment, a rotating drying drum, a feed trough into which said drum dips, and means for circulating the preheated yeast from said circulating compartment to said feed trough and thence back to said circulating compartment.

3. In drying apparatus, the combination of a rotating drying drum, a dip trough into which said drum dips for receiving the liquid material, a main equalizing blade for equaliaing the thickness oi' the film adhering. to the cylindrical surface of said drum, end scrapers having direct contact with the ends of the drum for removing the semi-liquid material from the ends of said drum, and auxiliary equalizing blades carried by said end scrapers and extending over and spaced slightly from the cylindrical surface of the drum for removing excess liquid material flowing from the ends of said drum around onto the cylindrical surface thereof.

4. In drying apparatus, the combination of a pre-heating chamber for pre-heating the liquid material, heating means for heating said chamber, agitating means in said pre-heating chamber for agitating the liquid material in said preheating chamber, a circulating chamber, means for heating said circulating chamber, spill means connecting said pre-heating chamber with said circulating chamber for supplying the warmer liquid from the upper levels in said pre-heating chamber to said circulating chamber, a dip trough, pump means for causing the liquid material to ilow from said circulating chamber to said dlp trough, a rotating drying drum dipping into said dip trough, a spill trough disposed adjacent to said dip trough for receiving excess liquid material from said dip trough, and means for causing said excess liquid material to now through a return path from said spill trough back to said circulating chamber.

ALBERT M. FISCHER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 279,219 Brown June 12, 1883 685,823 Cowin Nov. 5, 1901 929,178 Wentworth July 27, 1909 1,129,031 Wiesener Feb. 16, 1915 1,331,389 Sleeper Feb. 17, 1920 1,597,183 Devine Aug. 24, 1926 1,717,491 Bouda et al June 18, 1929 1,727,843 Tilley Sept. 10, 1929 1,853,451 Overton Apr. 12, 1932 1,873,833 Fell Aug. 23, 1932 1,957,146 Neubauer May l, 1934 2,259,606 Beardslee Oct. 21, 1941 

